Piping system in a vacuum degassing apparatus for molten metal

ABSTRACT

A piping system in a vacuum degassing apparatus for molten metal is described, which apparatus includes a ladle body suspended from movable suspension means disposed thereabove for receiving the molten metal poured from a lower end of an outlet trough of a furnace and adapted to be moved within a given vertical plane by said movable suspension means in accordance with the displacement of the lower end of said outlet trough which follows the process of pouring the molten metal; which piping system is characterized in that it comprises a mounting pipe fixedly secured onto an upper cover plate of said ladle body so as to communicate with an opening in said upper cover plate, a fixed pipe connected to evacuating means, and a plurality of movable pipes connected with each other and with said mounting pipe and said fixed pipe, respectively, via a plurality of pairs of vacuum-tightly coupled flanges disposed in parallel to said given vertical plane and rotationally slidable about the axes of said respective flange pairs so that said pipes may form a bendable vacuum tight piping system capable of extending and contracting within a plane in parallel to said given vertical plane. Further, an additional suspension means for suspending one of said movable pipes in such manner that the weight of the movable pipes and the flange pairs therebetween may not affect upon the weight balance of said ladle body, means for flexibly supporting an end portion near to said fixed pipe of said coupled movable pipes, means for quickly coupling said mounting pipe and the adjacent movable pipe, a favorable structure of the vacuum-tightly coupled slidable flanges, and automatically controlled movable truck means from which said one movable pipe is suspended via a wire rope, are described.

United States Patent [191 Yamazoe Mar. 26, 1974 PIPING SYSTEM IN A VACUUM DEGASSING APPARATUS FOR MOLTEN METAL [75] Inventor: Masao Yamazoe, Kobe, Japan [73] Assignee: Kabushiki Kaisha Osaka Shinkuukiki Seisakusho, Osaki-shi, Osaka-fu, Japan [22] Filed: Apr. 27, 1972 [21] Appl. No.: 248,155

[30] Foreign Application Priority Data May 14, 1971 Japan 46-32709 [52] U.S. Cl 266/13, 285/18, 285/226, 285/276 [51] Int. Cl. C21c 7/10 [58] Field of Search 266/13, 34 V; 75/49; 285/320, 364, DIG. 21, 276, 226

[56] References Cited UNITED STATES PATENTS 1,821,274 9/1931 Plummer 285/226 2,536,602 1/1951 Goett 285/D1G. 21 3,146,503 9/1964 Sickbcrt. 266/34 V 3,298,680 l/l967 Jablin t t 266/34 V 3,420,555 H1969 Faccou 285/276 3,473,830 10/1969 Haley 285/364 3,514,127 5/1970 Brooker 285/276 FOREIGN PATENTS OR APPLICATIONS 854,763 11/1960 Great Britain 285/DIG. 21 1,355,163 2/1964 France 75/49 Primary ExaminerGerald A. Dost Attorney, Agent, or Firm-Benoit Law Corporation [5 7] ABSTRACT A piping system in a vacuum degassing apparatus for molten metal is described, which apparatus includes a ladle body suspended from movable suspension means disposed thereabove for receiving the molten metal poured from a lower end of an outlet trough of a furnace and adapted to be moved within a given vertical plane by said movable suspension means in accordance with the displacement of the lower end of said outlet trough which follows the process of pouring the molten metal; which piping system is characterized in that it comprises a mounting pipe fixedly secured onto an upper cover plate of said ladle body so as to communicate with an opening in said upper cover plate, a fixed pipe connected to evacuating means, and a plurality of movable pipes connected with each other and with said mounting pipe and said fixed pipe, respectively, via a plurality of pairs of vacuum-tightly coupled flanges disposed in parallel to said given vertical plane and rotationally slidable about the axes of said respective flange pairs so that said pipes may form a bendable vacuum tight piping system capable of extending and contracting within a plane in parallel to said given vertical plane. Further, an additional suspension means for suspending one of said movable pipes in such manner that the weight of the movable pipes and the flange pairs therebetween may not affect upon the weight balance of said ladle body, means for flexibly supporting an end portion near to said fixed pipe of said coupled movable pipes, means for quickly coupling said mounting pipe and the adjacent movable pipe, a favorable structure of the vacuum-tightly coupled slidable flanges, and automatically controlled movable truck means from which :said one movable pipe is suspended via a wire rope, are described.

6 Claims, 10 Drawing Figures PAIENTEDMARZB 1974 3.799519 i FORCES APFUED TO (:0 Y

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L APPLIED TO 80 PIPING SYSTEM IN A VACUUM DEGASSING APPARATUS FOR MOLTEN METAL BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piping system associated with a ladle body in a vacuum degassing apparatus for molten metal in which harmful gases contained in the molten metal may be removed by means of an evacuating system.

2. Description of the Prior Art In general, during the process of pouring molten metal discharged from a furnace into a pony ladle and- /or an evacuated ladle, it is necessary to displace the ladle body in accordance with the variation of the inclination of the outlet trough of the furnace. Heretofore, as a piping system to be connected to the abovereferred displaceable ladle body, there has been manufactured a vacuum piping system which makes use of a flexible vacuum-tight pipe of bellows type. On the other hand, recently the amount of the material to be subjected to the degassing process has been increased and higher quality of products has become required. Consequently, a higher vacuum for use in the processing is required, and so, from the necessity of preventing the piping conductance from lowering, a larger diameter of vacuum pipe has become to be employed. However, the above-referred bellows type of pipe has less mechanical strength and is more fragile in view of its peculiar structural nature, and especially it is not suitable for rough handling as in the case of steel manufacturing work. More particularly, if a small impact force should be applied to the bellows type of pipe, or if molten steel should scattered towards the inner or outer surface of the bellows type of pipe, then deformation and/or cracks would be readily caused in the bellows type of pipe, which would result in reduction of the vacuum conductance. Furthermore, in case the diameter of the pipe is larger, the disadvantage caused by the deformation and/or cracks would be more enhanced, and also the manufacturing cost would be extremely raised.

One object of the present invention is to provide a piping system in a vacuum degassing apparatus for molten metal, which obviates all the disadvantages of the above-referred prior art piping system.

Another object of the present invention is to provide a quick coupling flange joint that is especially useful in the piping system according to the present invention though it is not limited to such uses only.

According to one aspect of the present invention, a piping system in a vacuum degassing apparatus for molten metal including a ladle body suspended from movable suspension means disposed thereabove for receiving the molten metal poured from a lower end of an outlet trough of a furnace adapted to be moved within a given vertical plane by said movable suspension means in accordance with the displacement of the lower end of said outlet trough which follows the process of pouring the molten metal, is characterized in that said piping system comprises a mounting pipe fixedly secured onto an upper cover plate of said ladle body so as to communicate with an opening in said upper cover plate, a relatively fixed pipe connected to evacuating means, and a plurality of movable pipes connected with each other and with said mounting pipe and said fixed pipe, respectively, via a plurality of pairs of vacuum-tightly coupled annular flanges disposed in parallel to said given vertical plane and rotationally slidable relative to each other about axes at rotation of said respective flange pairs extending perpendicularly to said vertical plane whereby said pipes form a flexible vacuum'tight piping system capable of extending and contracting with a plane in parallel to said given vertical plane.

BRIEF DESCRIPTION OF THE DRAWINGS The above-mentioned and other features and objects of this invention and the manner of attaining them will become more apparent and the invention itself will be best understood by reference to the following descrip tion of embodiments of the invention taken in conjunction with the accompanying drawings, in which:

FIG. I is a schematic front view of a vacuum degassing apparatus incorporating the piping system according to the present invention,

FIG. 2 is a schematic plan view of the vacuum degassing apparatus illustrated in FIG. 1,

FIG. 3 is a diagrammatic view of the two movable pipes in the piping system according to the present invention, for use in the mathematical analysis of the magnitude and the applied point of the vertical suspension force for one of the movable pipes,

FIG. 4 is an enlarged plane view of a further improved end portion of a fixed pipe in the piping system according to the present invention,

FIG. 5 is an enlarged side view of the fixed pipe por tion illustrated in FIG. 4,

FIG. 6 is a crosssection view showing the detailed structure of a pivotable supporting means associated with the fixed pipe portion illustrated in FIGS. 4 and 5,

FIG. 7 is a side view partially in cross-section of a quick coupling flange joint according to the present invention,

FIG. 8 is a cross-section view of a slidable vacuumtight flange pair to be used in the piping system illustrated in FIGS. 1 and 2,

FIG. 9 is a schematic side view of movable suspension means for a movable pipe in the piping system ac cording to the present invention, and

FIG. 10 is a schematic plan view of the means for detecting an inclination of the rope section suspending the movable pipe.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring now to FIGS. 1 and 2 of the drawings, molten metal 3 discharged through an outlet trough 2 of a furnace I is at first poured into a pony ladle 4. This pony ladle 4 is vacuum-tightly mounted on an upper cover plate 7 that is vacuum-tightly connected to a vacuum ladle body 5 via flanges 6. The ladle body 5 is provided with support rods 8 projecting from its outer wall in the direction perpendicular to the plane of the sheet as viewed in FIG. I, and hooks 10 of hangers 9, which are suspended from movable suspension means thereabove such as a crane (not shown), are engaged with said support rods 8, so that the entire ladle body may be vertically suspended as best seen in FIG. l. The evacuation of the inner space of the vacuum ladle body 5 is carried out through a mounting steel pipe section 11 fixedly secured onto the upper cover plate 7 of the vacuum ladle body 5 and subsequent series of steel pipes with a vacuum pump (not shown) connected at the farthest end of the steel pipe series. The mounting pipe section 11 having a 90 bend and another mounting pipe section 33 that is straight, form as a whole a mounting steel pipe, when they are coupled by means of a quick coupling flange joint 28 which will be more fully described later with reference to FIG. 7. Besides the mounting steel pipe 11, 33, the piping system comprises two movable steel pipes 15, 16 and a fixed steel pipe 17. The vacuum pump is to be connected to the right end of the fixed pipe 17 as viewed in FIGS. 1 and 2. The movable steel pipes 15 and 16 have substantially the same length and are provided with 90 bends at their respective opposite ends. The piping system also comprises three pairs of slidably and vacuum-tightly coupled flanges l2, l3 and 14 disposed in parallel to the plane of the sheet of FIG. 1, that is, in parallel to the plane in which the outlet trough 2 of the furnace and the suspended ladle body 5 are to be displaced. For

the purpose of illustration, phantom lines (101) and (102) in FIG. 2 indicate vertical planes which are parallel tothe plane in which the outlet trough (2) of the furnace and the suspended ladle body (5) are displaced during the process of pouring the molten metal. As apparent from FIGS. 1, 2, 7 and 8, each flange pair(l2), (13), (14) and (28) comprises annular flanges (44 and 45 in FIG. 7 or 55 and 66 in FIG. 8) which extend parallel to the parallel planes (101) and (102). Further for the purpose of illustration an axis of rotation (103) has been shown in FIG. 2 for the flange pair (12) and axes of rotation (104) and (105) have been shown for the flanges (l3) and (14), respectively. It will be noted that the axes of rotation (103), (104) and (105), about which the respective flange pairs rotate relative to each other, extend perpendicularly to the parallel plane (101) and/or (102). The flange pair 12 couples the mounting steel pipe 11 and 33 with the first movable steel pipe so that the flanges of the flange pair 12 may be rotated relative to each other about the center axis 103 of the flange pair 12 while maintaining the vacuum-tightness between the inner space of the steel pipes and theenvironmental atmosphere. Similarly, the flange pair 13 couples the first movable steel pipe 15 with the second movable steel pipe 16, and the flange pair 14 couples the second movable steel pipe 16 with the fixed steel pipe 17. The detailed structure of the slidably and vacuum-tightly coupled flange pair will be described later with reference to FIG. 8.

As described, the piping system according to the present invention forms a bendable piping system that is capable of extending and contracting within a plane in parallel to the vertical plane in which the outlet trough of the furnace as well as the ladle body are moved, without relying upon a bellows structure.

In the above-described piping system, the quick coupling flange joint 28 which connects the two sections 11 and 33 of the mounting steel pipe with each other, serves to quickly couple or disconnect the piping system to or from the ladle body 5 in response to a control from a remote station. More particularly, when it is nevcessitated to disconnect the ladle body 5 from the piping system, they are separated at this quick coupling flange joint 28, the mounting steel pipe section 11 being permanently secured to the ladle body 5, while the mounting steel pipe section 33 being permanently and displaceably connected to the remaining steel pipes 15, 16 and 17 via the slidable and vacuum-tight coupling flange pairs 12, 13 and 14 to form a bendable piping system.

In addition, it is to be noted that there is provided stopper means 27 between the pony ladle 4 and the vacuum ladle 5 for admitting the flow of molten metal from the pony ladle 4 to the vacuum ladle 5 or stopping the same flow.

Upon operation of the above-described degassing apparatus, at first the bendable piping system for evacuation of the vacuum ladle 5 including the mounting steel pipe section 33, movable steel pipes 15 and 16, fixed steel pipe 17 and the slidable and vacuumtight coupling flange pairs 12, 13 and 14, is coupled to the mounting steel pipe section 11 fixedly secured to the upper cover plate 7 of the vacuum ladle 5 with the aid of the quick coupling flange joint (28). Then the vacuum pump (not shown) is started into operation to evacuate the inner space of the vacuum ladle 5.

Through operation of a crane (not shown) provided above the degassing apparatus and suspending the ladle body 5 via a rope and a hanger 9, the pony ladle 4 and the vacuum ladle 5 are brought to the position just beneath the end of the outlet trough 2 of the furnace 1. When the vacuum pressure within the vacuum ladle 5 has reached a predetermined value, tapping is started from the furnace 1 via the outlet trough 2 into the pony ladle 4. As soon as an adequate amount of molten metal is filled in the pony ladle 4, the stopper means 27 is actuated through a remote control to make the molten metal within said pony ladle 4 flow down into the vacuum ladle 5. During this flow down, harmful gases contained in the molten metal are extracted with the aid of the vacuum formed in the vacuum ladle 5, and then discharged outwardly through the evacuating system, not shown.

As the tapping from the furnace 1 proceeds, the outlet trough 2 is more inclined, and so the end of the outlet trough 2 is displaced in the oblique left-downward direction as viewed in FIG. 1. In accordance with the displacement of the lower end of the trough 2, the crane (not shown) located above the ladle body 5 is operated so that the ladle body 5 may be displaced in the direction shown by an arrow a shown in FIG. 1 and thereby the inlet opening of the pony ladle 4 may always take the most favorable position for receiving the molten metal poured through the outlet trough 2. The most favorable position exists substantially just beneath the lower end of the outlet trough 2.

After thetapping of the molten metal from the furnace 1 has been completed and the vacuum ladle 5 has been filled with the molten metal, if necessary, an inert gas such as argon is blown into the vacuum ladle 5 from its bottom to achieve deoxydation of the molten metal, or an operation for adding alloying materials and the like is carried out. After these operations have been finished, a main valve (not shown) of the evacuating system is closed and an air introduction valve 20 mounted on the fixed steel pipe 17 is opened to introduce air into the vacuum ladle 5. Simultaneously therewith, the piping system is quickly disconnected from the vacuum ladle 5 at the quick coupling flange joint 28 through an operation of hydraulic actuating means located remotely from said quick coupling flange joint 28. Then the disconnected ladle body 5 is transferred to a casting station with the aid of the operation of the crane provided thereabove.

From the above description it will be apparent that the vacuum piping system constructed according to the present invention is mechanically stronger and less fragile than the bellows type of piping, even if it is designed and constructed with a larger diameter so as to present a higher fluid conductance to meet the requirement of a high vacuum to be maintained in the vacuum ladle. And yet, the vacuum piping system constructed according to the present invention is bendable and capable of extending and contracting within a vertical plane in parallel to the vertical plane in which the outlet trough 2 and the ladle body 5 are displaced, owing to the provision of the slidably and vacuum-tightly coupled flange pairs 12, 13 and 14.

While two movable steel pipes and 16 have been used in the embodiment illustrated in FIGS. 1 and 2, it will be obvious that more than two movable steel pipes can be used together with the slidably and vacuumtightly coupled flange pairs to form a continuous bendable vacuum piping system.

Since the above-described ladle assembly consisting of the pony ladle 4 and the vacuum ladle 5 is supported by means of the support rods projecting laterally from its side wall and the associated hooks of the hanger 9, the ladle assembly may possibly incline in either direction during the process of pouring the molten metal into the ladle body, or when the vacuum piping system is connected to or disconnected from the ladle assembly. As is well-known to those skilled in the art, it is extremely harmful and must be avoided that the ladle assembly 4, 5 is inclined due to the above-referred causes. In order to meet these requirement, the ladle assembly 4, 5 is designed so that the centers of gravity of the ladle assembly when it is empty and when it is filled with the molten metal to any arbitrary level must exist on the same vertical plane, provided that the vacuum piping system is disconnected from the ladle assembly at the quick coupling flange joint 28, and the support rods 8 are provided on the outer wall of the vacuum ladle 5 within said same vertical plane.

Furthermore, we have discovered as a result of mathematical analysis that the weight balance of the ladle assembly 4, 5 is not disturbed by connecting the vacuum piping system to said ladle assembly, if a particular point on one of the movable steel pipes is vertically suspended with a particular vertical force. We have obtained the necessary condition for the case of two movable steel pipes 15 and 16 each having a straight pipe body of equal length l and 90 bends at its opposite ends which are directly connected to the vacuum-tight slidable flanges, as shown in FIGS. 1 and 2.

Now the mathematical analysis will be given as follows: In order to obtain the above-described balanced condition, it will be apparent that the vacuum piping system consisting of the mounting pipe section 33 including one of the coupling flange in the quick coupling flange joint 28, the movable steel pipes 15 and 16, the fixed pipe 17, and the slidable vacuum-tight flange pairs 12, 13 and 14, must be in a mechanically balanced condition by itself with the aid of the suspending vertical force exerted upon the movable pipe 15 at one point thereon. If the above condition is satisfied, when the ladle assembly 4, 5 is connected to said vacuum piping system via the quick coupling flange joint 28, they would exert no force upon each other, and consequently the respective balanced condition would be maintained so as not to cause the inclination of the ladle assembly 4, 5.

For simplicity of analysis, the bendable portion of the piping system is diagrammatically represented by means of segments BD and DC in FIG. 3,. The points B, D and C represent the centers of the slidable vacuum-tight flange pairs (l2), (l3) and (14), respectively, and the point A represents the point on the movable pipe 15 where a vertical suspension force P is applied. Apparently, the segments BD and DC represent the movable pipes 15 and 16, respectively.

Now let us consider the balanced condition of this mechanical system. For use in the mathematical analysis, various quantities are represented by the following reference characters:

Weight of the slidable vacuum tight flange pair 12 or l3 2W,

Weight of the mounting pipe section 33 including the W; Weight of the flange in the quick coupler 28 secured to said pipe section 33 Length of the movable pipe 15 or 16 1 Weight of the movable pipe l5 or 16 W Angle between the direction of BD and the horizon [3 Angle between the direction of DC and the horizon 0:

Considering the forces exerted upon the movable pipe 16, that is, the segment DC, it is apparent in view of the symmetrical structure about the center of gravity G that a gravitational force W at the center of gravity G and, gravitational forces W for the respective flange members at the end points D and C are balanced with a upward vertical external force equal to W 12 W exerted at the end point C and a similar upward vertical external force equal to W /2 W exerted at the end point D. As a result of reaction from the movable pipe 16, the movable pipe 15, that is, the segment FD is applied with a downward vertical force equal to W /2 W and a gravitational force W for the slidable vacuum-tight flange member at the poimt D. Consequently, as shown in FIG. 3, the movable pipe 15 including the mounting pipe section 33 and the associated quick coupling flange member, that is, the segment B D is applied with the following vertical forces:

Weight of pair (12) and (downward) pair (13) and the external force exerted by the movable pipe (16).

Now we can set up equations of balanced conditions with respect to the moment about the point A and with respect to the sum of the vertical components of the forces as follows:

From the first equation, we can obtain an equation giving the distance x between the point A and the point D as follows:

Also the vertical suspension force P required for the balanced condition can be obtained from the second equation as follows:

From the above-described mathematical analysis, it will be seen that if a suspending point A is provided on the segment BD, that is, on the movable pipe 15 at a point apart from the point D by the distance x given by Eq. 1 above and if a suspension force P given by Eq. 2 above is applied to said suspending point A, then upon connecting the vacuum piping system to the ladle assembly 4, via the quick coupling flange joint 28, neither vertical nor horizontal force component is exerted by the piping system upon the ladle assembly, and consequently, the balanced condition of the ladle assembly is not disturbed by the connection or disconnection of the piping system. Furthermore, in view of the fact that the above equations 1 and 2 include neither the angle B nor the angle B, it is obvious that the balanced condition of the piping system can be maintained at any arbitrary position of the piping system during its deformation and displacement in accordance with the displacement of the ladle assembly 4 and 5 regardless of the change of the angles a and 62 Referring again to FIGS. 1 and 2, in the illustrative degassing apparatus, the means for suspending the movable steel pipe at one point thereon, consists of a wire rope 18, a strip member 29 having its opposite ends fixedly secured to the flanges at the opposite ends of the movable pipe 15 and having a support pin 32 projected therefrom, a mounting member 30 affixed to the lower end 19 of the wire rope l8 and pivotably engaged with said support pin 32, a truck 24 having a support frame 23 for a pulley 21 mounted thereon and adapted to travel forth and back on rails 26 with the aid of wheels 25, said wire rope 18 being engaged with said pulley 21, and a counter balance weight 22 fixedly secured to the other end of said wire rope l8 and suspended on the opposite side of said pulley 21. As will be readily seen, the distance between the support pin 32 and the center axis of the slidable vacuum-tight flange pair 13 is selected equal to x as given by Eq. 1, and the weight of the counter balance weight 22 is chosen equal to P as given by Eq. 2. It is to be noted that when the ladle assembly 4 and 5 is displaced by means of a crane in accordance with the movement of the outlet trough 2, the movable steel pipe 15 and thus the support pin 32 are also displaced, but since the track 24 can travel along the rails 26 following the displacement of the support pin 32, the wire rope 18 between the pulley 21 and the mounting member 29 would be always maintained vertical, and thereby it is assured that the suspension force applied to the support pin 32 is always directed in the vertical direction.

The aforementioned vacuum degassing apparatus can operate satisfactorily, if provision is made such that during the operation of the apparatus the ladle assembly 4 and 5 may not rotate about its vertical axis or may not swing in perpendicular to the vertical plane in which the outlet trough 2 and the ladle assembly are displaced as by suspending the ladle assembly with a plurality of wire ropes. However, since the ladle assembly is normally suspended with a single wire rope, it is inevitable in the course of displacement of the ladle body following the movement of the outlet trough 2 that the ladle assembly 4 and 5 is more or less subjected to a spin motion about the wire rope and/or a swing motion in perpendicular to the vertical plane in which the outlet trough 2 and the ladle assembly are displaced.

As a result, the bendable piping system which can extend and contract only in a given vertical plane, is forced to swing in perpendicular to said given vertical plane. This would cause a disadvantage that a large torque is applied to the fixing portion of the fixed steel pipe 17, resulting in vacuum leakage and/or destruction of the pipes and the slidable vacuum-tight flange pairs.

In order to obviate the above-mentioned disadvantage, according to another aspect of the present invention, the fixed steel pipe 17 can be constructed so as to release the torque which may be caused by the spin motion and/or the swing motion of the ladle body as shown in FIGS. 4 through 6. In FIGS. 4 and S, the fixed steel pipe 17 illustrated in FIGS. 1 and 2 is divided into two pipe sections 17 and 17", and these pipe sections are vacuum-tightly connected with a flexible pipe section 34 of bellows type. Around the pipe sections 17 and 17" are fixedly secured ring members 36 and 36', respectively. Each of the ring members 36 or 36 is pivotably supported on a fixed base by means of a supporting device consisting of a shaft 38 or 38 fixedly secured to said ring member and having a conical fitting portion 37 and a receiving pedestal 40 provided with a conical receiver surface 39, as shown in FIG. 6. In addition, on the outer surface of the fixed pipe section 17 between the ring member 36 and the flexible pipe section 34 are fixedly secured cup-shaped spring receiver seats 41 at its diametrically opposed lateral positions, and springs 44 are interposed between said spring receiver seats 41 and similar cup-shaped spring receiver seats 43 mounted on the opposed wall surface of a pit 42 in which the fixed pipe assembly 17', 34, 17" is accomodated. Owing to the above-described structure of the fixed pipe assembly 17, 34, 17", when a torque is applied to the fixed pipe assembly because of the spin motion and/or the swing motion of the ladle body, the fixed pipe sections 17 and 17" can swing about its pivotal shaft 38 and 38, respectively, and the flexible pipe section 34 can bend so as to vacuum-tightly connect these displaced pipe sections 17 and 17". Therefore, harmful forced stress is not applied to any part of the fixed pipe assembly, and thereby the above-described disadvantage which may occur when a rigid fixed pipe 17 is used, may be obviated. When the rotational or swing displacement of the ladle assembly has been reduced to zero, the resilient support means consisting of the spring seats 41, 43 and the spring 44 serves to restore the fixed pipe assembly 17', 34, 17 to its original position and configuration.

As in the case of the vacuum degassing apparatus comprising a ladle assembly and a vacuum piping system shown in FIGS. 1 and 2, generally in an apparatus which essentially necessitates the use of a piping system of larger diameter, where the connection and disconnection of the piping system are often necessitated for each operation of the apparatus, and where the con necting and disconnecting operations involve complex handling as is the case of the connection and disconnection between the vacuum ladle and the evacuating piping system upon degassing the tapped molten metal, heretofore a bolt-fastening system or a clutch system has been employed in order to facilitate the operation. In addition, since the above described system had a disadvantage that the structure is more complex and more expensive, a fastening system employing a steel wire rope and a fastener in combination, has been used. This system still had a disadvantage that as the diameter of the piping system is increased the weight thereof is also increased accordingly, and consequently the operation of winding the steel wire rope around the outer periphery of the flange and fastening the same becomes more difficult.

In view of the above-described disadvantages of the prior art, the present invention provide a quick coupling flange joint which enables a pair of flanges to be engaged and disengaged in a very simple and reliable manner through a remote control. This quick coupling flange joint can be used as the flange joint 28 between the mounting pipe sections 11 and 33 as illustrated in FIGS. 1 and 2, but it is to be noted that the quick coupling flange joint according to the present invention as described hereinafter with reference to FIG. 7 may be used anywhere where quick and reliable connection and disconnection between flanged pipes are required.

Referring now to FIG. 7, the mounting pipe section 11 on the ladle side and the mounting pipe section 33 on the piping side have vacuum-tightly engageable flanges 44', 45 fixedly secured to their joint ends. On the outside of one flange 45 are pivotably mounted a plurality of squill vices 48 via mounting bracket 46 and pivotal pins 47 along the circumference of the flange 45. A hydraulic cylinder 54 is connected between the outer wall of the mounting pipe section 33 and the C- shaped body of each of the squill vices 48 via a pivotal pin 50 on the C'shaped body and a pivotal pin 52 on a bracket 53 secured on the outer wall of the mounting pipe section 33. As will be readily seen from FIG. 7, when the hydraulic cylinder 54 is in its extended state, the squill vice 48 takes its engaging position (shown by a solid line) adapted to bridge over the engaged two flanges 44 and 45, whereas when the hydraulic cylinder 54 is in its contracted state, the squill vice 48 takes its disengaging position (shown by a dash-dot line) where the C-shaped body is erected apart from the engaged two flanges 44' and 45 for enabling them to disengage from each other. In addition, the C-shaped body of the squill vice 48 is provided with another hy draulic cylinder 49 at its free end portion for applying I a pressure to the vice head to fasten the engaged two flanges 44 and 45 when the squill vice 48 is in its engaging position. All the hydraulic cylinders 40 and 54 are actuated through hydraulic piping circuit 120 and 121 from a remote control station 122 for the quick coupling flange joint 28.

Since the quick coupling flange joint according to the present invention is constructed as described above, one can couple two pipes together in a simple and reli able manner from a remote control station. Therefore, in dangerous operations for handling high temperature molten metal which must be repeated frequently, as in the case of degassing operations during tapping of mo]- ten metal from a furnace or in the case of recycled degassing operations, the above-described quick coupling flange joint according to the present invention is especially useful and effective. Furthermore, when the diameter of the piping is increased, it is only necessary to increase the number of the squill vices 48 and asso' ciated hydraulic cylinders 54 to be arranged along the circumference of the flange 45.

In FIG. 8, is illustrated one preferred structure of the above-referred slidable and vacuum-tight flange pair 12, 13 or 14. A flange 55 is fixedly secured to an end ofa movable pipe 15, while another flange 66 is fixedly secured to an end of a movable pipe 16. An annular projection 56 extends axially from the opposing face of the flange 55 towards the flange 66. while another annular projection 82 extends axially from the opposing face of the flange 66 towards the flange 55. The annular projection 82 has a smaller diameter than the annular projection 56, and within the annular space formed between the annular projections 56 and 82 and between the flanges 55 and 66 is mounted an oil seal 69 or an Willson seal (not shown) which serves as a rotationally slidable vacuum seal. The outside wall of the Oil seal 69 forms a fixed seal with the aid of an O-ring 80, while the inside of the oil seal 69 forms a slidable seal with respect to a finished outer cylindrical surface of the annular projection 82 of the flange 66 with the aid of a lip 81 of the oil seal 69. Outside of the annular projection 56, a ball bearing assembly is mounted between the opposed faces of the flanges S5 and 66. More particularly, an inner ring 57 of the ball bearing is fixedly secured to the opposing face of the flange 55 by means ofa bolt 58 and a nut 59, while an outer ring 62 of the same ball bearing is fixedly secured to the opposing face of the flange 66 by means of a bolt 64 and a nut 65. The inner and outer rings 57 and 62 are deeply grooved at 63 and 67 on their opposed cylindrical sur faces to receive steel balls 60, and in the narrow annular space between the inner and outer rings 57 and 62 is interposed a ball retainer ring 61.

Since the slidable and vacuum-tight flange pair 12, 13 or 14 is constructed as described above, not only the mechanical loading in the radial direction but also the mechanical loading in the thrust direction, can be well borne by the ball bearing means having deep grooves for receiving the steel balls. On the other hand, the rotationally slidable vacuum seal means 69 can maintain the vacuum-tightness between the inner space of the piping system and the environmental atmosphere without being subjected to any mechanical loading. Therefore, such type of slidable vacuum-tight flange pairs are very useful when applied to the vacuum degassing apparatus as illustrated in FIGS. 1 and 2, in that the bendable vacuum piping system provided with such flange pairs between the movable pipes is capable of withstanding a compression pressure, a tensioning load, a bending moment, etc. to be generated therein, that the necessary rotational sliding can be achieved smoothly while maintaining the vacuum-tightness, and that the slidable vacuum-tight flange pair can be manufactured at low cost.

Referring now to FIGS. 9 and 10 of the drawings, a preferable structure of the track 24 having a support frame 23 for a pulley 21 mounted thereon as shown in FIGS. 1 and 2, is illustrated in detail. In this structure, in order to cause the track 24 to travel along the rails 26 so as to exactly follow the displacement of the support pin 32 on the movable pipe when the ladle assembly 4 and 5 is displaced, the track 24 is provided with reversible driving means including a reversible reduced speed motor 68, means for detecting an inclination of the wire rope section 18 between the pulley 21 and the support pin 32, and control means responsive to detection of the inclination of said wire rope section 18 for actuating the reversible driving means. According to one preferred embodiment, the above-referred means are so designed that the track 24 may follow the movement of the support pin 32 even when less than one-tenth of the horizontal force is applied to the track 24 in the horizontal direction through the wire rope section 18, that is, even when an inclination of the wire rope section 18 with respect to the horizontal force which is less than one-tenth has been detected.

More particularly, the reversible driving means for the track 24 comprises a reversible reduced speed motor 68, a sprocket 70, a chain 71 another sprocket 72, a shaft 73 and wheels 25 as shown in FIG. 9. A steel wire rope 18 having one end connected to the support pin 32 of the movable pipe 15 via the mounting member 30, is engaged with a pulley 21 that is rotatably supported at the extremity of an arm 23 projecting obliquely in the outward and upward direction from the track 24, so that the steel wire rope may be led to a counter balance weight 22 suspended on the opposite side of the track 24 via a similar pulley (See FIGS. 1 and 2). The means for detecting an inclination of the wire rope section 18 between the pulley 21 and the support pin 32 comprises a Y-shaped horizontal arm 74 that is pivotably supported from the bottom surface of the track 24 via a pivotal pin 75. At the tips of the Y- shaped branches of the horizontal arm 74 are rotatably mounted guide rollers 76, 76, so that the steel wire rope 18 may be interposed between these guide rollers, as best seen in FIG. 10. The outer end, i.e., the base end of the horizontal arm 74 is held by means of similar springs 77, 77 from its opposite sides, so as to maintain the horizontal arm at its neutral position when the wire rope 18 exerts no force upon either one of the guide rollers 76, 76. At the base end of the horizontal arm 74 is also mounted an actuator roller 78 that is adapted to engage with either one of limit switches 79, 79 provided on the opposite sides of the actuator roller 78, when the horizontal arm 74 is displaced in either direction via the guide roller 76 in response to an inclination of the wire rope 18.

The respective limit switches 79, 79 are connected in the energizing circuit for the reversible reduced speed motor 68 so as to energize a forward drive power supply branch and a backward drive power supply branch, respectively. The circuit connection is made in such manner that when an inclination of the wire rope 18 in one direction is detected by an angular displacement of the horizontal arm 74 about the pivotal pin 75, the reversible reduced speed motor 68 may be energized so as to drive the track 24 in the direction for reducing the inclination of the wire rope 18.

From the above description, it will be readily seen that the actuator roller 78 and the limit switches 79, 79 in combination form the control means responsive to detection of the inclination of the wire rope section for actuating the reversible driving means.

According to this embodiment of the suspension means for the movable pipe 15, the track 24 from which the movable pipe 15 is suspended, is positively driven by the reversible reduced speed motor 68 in response to detection of a small inclination of the wire rope 18, rather than driven by a horizontal component of the force exerted through the wire rope 18. Therefore, when the ladle assembly is moved and consequently the movable pipe 15 is also displaced, the track 24 can precisely and sensitively follow the displacement of the movable pipe 15 so as to keep the wire rope section 18 always vertical. This is helpful for exactly satisfying the balanced condition for the piping system as expressed by preceding Equations 1 and 2. As a result, the ladle assembly 4 and 5 coupled to the piping system can always maintain its weight balance exactly during the movement in accordance with the displacement of the outlet trough 2 of the furnace 1.

Since many changes could be made in the above construction and widely different embodiments of this in vention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

l. A piping system in a vacuum degassing apparatus for molten metal including a ladle body suspended from movable suspension means disposed thereabove for receiving the molten metal poured from a lower end of an outlet trough of a furnace and adapted to be moved within a given vertical plane by said movable suspension means in accordance with the displacement of the lower end of said outlet trough which follows the process of pouring the molten metal; characterized in that said piping system comprises a mounting pipe fixedly secured onto an upper cover plate of said ladle body so as to communicate with an opening in said upper cover plate, a relatively fixed pipe connected to evacuating means, and a plurality of movable pipes connected with each other and with said mounting pipe and said fixed pipe, respectively, via a plurality of pairs of slidably and vacuum-tightly coupled annular flanges disposed in parallel to said given vertical plane and rotationally slidable relative to each other about axes of rotation of said respective flange pairs extending perpendicularly to said vertical plane whereby said pipes form a flexible vacuum-tight piping system capable of extending and contracting within a plane in parallel to said given vertical plane.

2. A piping system in a vacuum degassing apparatus for molten metal including a ladle body suspended from movable suspension means disposed thereabove for receiving the molten metal poured from a lower end of an outlet trough of a furnace and adapted to be moved within a given vertical plane by said movable suspension means in accordance with the displacement of the lower end of said outlet trough which follows the process of pouring the molten metal; characterized in that said piping system comprises a mounting pipe fixedly secured onto an upper cover plate of said ladle body so as to communicate with an opening in said upper cover plate, a relatively fixed pipe connected to evacuating means, and a plurality of movable pipes connected with each other and with said mounting pipe and said fixed pipe, respectively, via a plurality of pairs of slidably and vacuum-tightly coupled flanges disposed in parallel to said given vertical plane and rota tionally slidable about the axes of said respective flange pairs, said piping system being further characterized in that said plurality of movable pipes include two movable pipes each having a straight pipe body of equal length l and 90 bends at its opposite ends which are directly connected to predetermined ones of said vacuum-tight slidable flanges, that said mounting pipe includes two sections that can be freely connected to and disconnected from each other, that said piping system includes second suspension means adapted to suspend the one of said two movable pipes located nearer to said mounting pipe at a point a distance of x apart in the lengthwise direction of said one movable pipe from the center of the flange pair between said two movable pipes with a vertical force P, and that said distance x and said vertical force P satisfy the following conditions:

where 2W represents the weight of the flange pair, W represents the weight of each movable pipe, and W represents the weight of one section of said mounting pipe nearer to said movable pipes.

3. A piping system in a vacuum degassing apparatus for molten metal including a ladle body suspended from movable suspension means disposed thereabove for receiving the molten metal poured from a lower end of an outlet trough of a furnace and adapted to be moved within a given vertical plane by said movable suspension means in accordance with the displacement of the lower end of said outlet trough which follows the process of pouring the molten metal; characterized in that said piping system comprises a mounting pipe fixedly secured onto an upper cover plate of said ladle body so as to communicate with an opening in said upper cover plate, a relatively fixed pipe connected to evacuating means, and a plurality of movable pipes connected with each other and with said mounting pipe and said fixed pipe, respectively, via a plurality of pairs of slidably and vacuum-tightly coupled flanges disposed in parallel to said given vertical plane and rotationally slidable about the axes of said respective flange pairs, said piping system being further characterized in that said relatively fixed pipe consists of a main pipe section, a terminal pipe section directly connected to said vacuum-tight slidable flange pair and a bellows section vacuum-tightly connected between said main pipe section and said terminal pipe section, that said main pipe section is supported at one end adjacent to said bellows section pivotably about a vertical axis, and that said terminal pipe section is pivotably supported at one point about a vertical axis and also resiliently supported at laterally and diametrically opposed points located between said one point and one end adjacent to said bellows section.

4. A piping system in a vacuum degassing apparatus for molten metal as claimed in claim 1, further characterized in that said mounting pipe includes two sections interconnected via a quick coupling flange jount, which includes vacuum-tightly engageable flanges each connected fixedly to a jount end of said respective sections, a plurality of squill vices disposed along the circumference of one of said flanges, each of said squill vices having a C-shaped body and means for connecting one end of the C-shapedrbody pivotably to said one flange, a plurality of firsthydraulic cylinder means equal in num her to said squill vices interconnected between the pipe section having said one flange and said C-shaped bodies of the respective squill vices for displacing said squill vices at said pivotable connecting means between their engaging position adapted to bridge over'the engaged two flanges and their disengaging position for enabling the two flanges to be disengaged, each squill vice having a squill vice head and second hydraulic cylinder means for actuating said vice head, and hydraulic actu ating system for controlling the operation of said first hydraulic cylinder means and said second hydraulic cylinder.

5. A piping system in a vacuum degassing apparatus for molten metal including a ladle body suspended from movable suspension means disposed thereabove for receiving the molten metal poured from a lower end of an outlet trough of a furnace and adapted to be moved within a given vertical plane by said movable suspension means in accordance with the displacement of the lower end of said outlet trough which follows the process of pouring the molten metal; characterized in that said piping system comprises a mounting pipe fixedly secured onto an upper cover plate of said ladle body so as to communicate with an opening in said upper cover plate, a relatively fixed pipe connected to evacuating means, and a plurality of movable pipes connected with each other and with said mounting pipe and said fixed pipe, respectively, via a plurality of pairs of slidably and vacuum-tightly coupled flanges disposed in parallel to said given vertical plane and rotationally slidable about the axes of said respective flange pairs, said piping system being further characterized in that each of said vacuum-tightly coupled flange pairs consists of a first flange fixedly secured to an end of one pipe and having a first annular projection extending axially from the opposing face of the flange, a second flange fixedly secured to an end of the other pipe and having a second annular projection extending axially from the opposing face of said second flange, said second annular projection having a smaller diameter than said first annular projection, ball bearing means having its inner ring member secured to the opposing face of said first flange and its outer ring member secured to the opposing face of said second flange, and slidable vacuum seal means mounted within the annular space between said first annular projection and said second annular projection, whereby the mechanical loading between said one pipe and said other pipe may be borne via said ball bearing means and the vacuumtightness between the inner space of the pipe system and the environmental atmosphere may be maintained by means of said slidable vacuum seal means while admitting the relative rotation of the flanges and their associated pipes about the center axis of said flanges.

6. A piping system'in a vacuum degassing apparatus for molten metal including a ladle body suspended from movable suspension means disposed thereabove for receiving the molten metal poured from a lower end of an outlet trough of a furnace and adapted to be moved within a given vertical plane by said movable suspension means in accordance with the displacement of the lower end of said outlet trough which follows the process of pouring the molten metal; characterized in that said piping system comprises a mounting pipe fixedly secured onto an upper cover plate of said ladle body so as to communicate with an opening in said upper cover plate, a relatively fixed pipe connected to evacuating means, and a plurality of movable pipes connected with each other and with said mounting pipe and said fixed pipe, respectively, via a plurality of pairs of slidably and vacuum-tightly coupled flanges disposed in parallel to said given vertical plane and rotationally slidable about the axes of said respective flange pairs, said piping system being further characterized in that said piping system includes a second suspension means adapted to vertically suspend one of said movable pipes at one point thereon, and comprising guide means, a truck adapted to travel forth and back along said guide means, reversible driving means for driving said truck, a rope having one end connected to said one point on the movable pipe and the other end connected to a counterbalance weight, pulley means mounted on said truck for supporting said rope, means for detecting an inclination of the rope section between said pulley means and said one point on the novable pipe with respect to the vertical, and control means responsive to detection of the inclination of said rope section for actuating the reversible driving means for said truck whereby to reduce the inclination of said rope section.

33 3? UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3.799.5l 9 Dated M h 25, 1974 Inventofls) Masao Yamazoe It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Page l Item ['73] "Osaki-shi" should be -0saka-sh1'-; The formula in 1 column 7, line 3, should read P (2w N The Formula in column 7, line 9, should read 4W N 2W lhe formula in column l3, line 26, should read 4W N 2W The formula in column l3, line 27, should read 8W 3w 2w Signed and sealed this 17th day of September 1974. v

(SEAL) Attest;

McCOY M. GIBSON JR. Cc, MARSHALL DANN Attesting Officer Commissioner of Patents 

1. A piping system in a vacuum degassing apparatus for molten metal including a ladle body suspended from movable suspension means disposed thereabove for receiving the molten metal poured from a lower end of an outlet trough of a furnace and adapted to be moved within a given vertical plane by said movable suspension means in accordance with the displacement of the lower end of said outlet trough which follows the process of pouring the molten metal; characterized in that said piping system comprises a mounting pipe fixedly secured onto an upper cover plate of said ladle body so as to communicate with an opening in said upper cover plate, a relatively fixed pipe connected to evacuating means, and a plurality of movable pipes connected with each other and with said mounting pipe and said fixed pipe, respectively, via a plurality of pairs of slidably and vacuum-tightly coupled annular flanges disposed in parallel to said given vertical plane and rotationally slidable relative to each other about axes of rotation of said respective flange pairs extending perpendicularly to said vertical plane whereby said pipes form a flexible vacuum-tight piping system capable of extending and contracting within a plane in parallel to said given vertical plane.
 2. A piping system in a vacuum degassing apparatus for molten metal including a ladle body suspended from movable suspension means disposed thereabove for receiving the molten metal poured from a lower end of an outlet trough of a furnace and adapted to be moved within a given vertical plane by said movable suspension means in accordance with the displacement of the lower end of said outlet trough which follows the process of pouring the molten metal; characterized in that said piping system comprises a mounting pipe fixedly secured onto an upper cover plate of said ladle body so as to communicate with an opening in said upper Cover plate, a relatively fixed pipe connected to evacuating means, and a plurality of movable pipes connected with each other and with said mounting pipe and said fixed pipe, respectively, via a plurality of pairs of slidably and vacuum-tightly coupled flanges disposed in parallel to said given vertical plane and rotationally slidable about the axes of said respective flange pairs, said piping system being further characterized in that said plurality of movable pipes include two movable pipes each having a straight pipe body of equal length l and 90* bends at its opposite ends which are directly connected to predetermined ones of said vacuum-tight slidable flanges, that said mounting pipe includes two sections that can be freely connected to and disconnected from each other, that said piping system includes second suspension means adapted to suspend the one of said two movable pipes located nearer to said mounting pipe at a point a distance of x apart in the lengthwise direction of said one movable pipe from the center of the flange pair between said two movable pipes with a vertical force P, and that said distance x and said vertical force P satisfy the following conditions: x (4W1 + W2 + 2W3)/(8W1 + 3W2 + 2W3).l and P 8W1 + 3W2 + 2W3/2, where 2W1 represents the weight of the flange pair, W2 represents the weight of each movable pipe, and W3 represents the weight of one section of said mounting pipe nearer to said movable pipes.
 3. A piping system in a vacuum degassing apparatus for molten metal including a ladle body suspended from movable suspension means disposed thereabove for receiving the molten metal poured from a lower end of an outlet trough of a furnace and adapted to be moved within a given vertical plane by said movable suspension means in accordance with the displacement of the lower end of said outlet trough which follows the process of pouring the molten metal; characterized in that said piping system comprises a mounting pipe fixedly secured onto an upper cover plate of said ladle body so as to communicate with an opening in said upper cover plate, a relatively fixed pipe connected to evacuating means, and a plurality of movable pipes connected with each other and with said mounting pipe and said fixed pipe, respectively, via a plurality of pairs of slidably and vacuum-tightly coupled flanges disposed in parallel to said given vertical plane and rotationally slidable about the axes of said respective flange pairs, said piping system being further characterized in that said relatively fixed pipe consists of a main pipe section, a terminal pipe section directly connected to said vacuum-tight slidable flange pair and a bellows section vacuum-tightly connected between said main pipe section and said terminal pipe section, that said main pipe section is supported at one end adjacent to said bellows section pivotably about a vertical axis, and that said terminal pipe section is pivotably supported at one point about a vertical axis and also resiliently supported at laterally and diametrically opposed points located between said one point and one end adjacent to said bellows section.
 4. A piping system in a vacuum degassing apparatus for molten metal as claimed in claim 1, further characterized in that said mounting pipe includes two sections interconnected via a quick coupling flange jount, which includes vacuum-tightly engageable flanges each connected fixedly to a jount end of said respective sections, a plurality of squill vices disposed along the circumference of one of said flanges, each of said squill vices having a C-shaped body and means for connecting one end of the C-shaped body pivotably to said one flange, a plurality of first hydraulic cylinder means equal in number to said squill vicEs interconnected between the pipe section having said one flange and said C-shaped bodies of the respective squill vices for displacing said squill vices at said pivotable connecting means between their engaging position adapted to bridge over the engaged two flanges and their disengaging position for enabling the two flanges to be disengaged, each squill vice having a squill vice head and second hydraulic cylinder means for actuating said vice head, and hydraulic actuating system for controlling the operation of said first hydraulic cylinder means and said second hydraulic cylinder.
 5. A piping system in a vacuum degassing apparatus for molten metal including a ladle body suspended from movable suspension means disposed thereabove for receiving the molten metal poured from a lower end of an outlet trough of a furnace and adapted to be moved within a given vertical plane by said movable suspension means in accordance with the displacement of the lower end of said outlet trough which follows the process of pouring the molten metal; characterized in that said piping system comprises a mounting pipe fixedly secured onto an upper cover plate of said ladle body so as to communicate with an opening in said upper cover plate, a relatively fixed pipe connected to evacuating means, and a plurality of movable pipes connected with each other and with said mounting pipe and said fixed pipe, respectively, via a plurality of pairs of slidably and vacuum-tightly coupled flanges disposed in parallel to said given vertical plane and rotationally slidable about the axes of said respective flange pairs, said piping system being further characterized in that each of said vacuum-tightly coupled flange pairs consists of a first flange fixedly secured to an end of one pipe and having a first annular projection extending axially from the opposing face of the flange, a second flange fixedly secured to an end of the other pipe and having a second annular projection extending axially from the opposing face of said second flange, said second annular projection having a smaller diameter than said first annular projection, ball bearing means having its inner ring member secured to the opposing face of said first flange and its outer ring member secured to the opposing face of said second flange, and slidable vacuum seal means mounted within the annular space between said first annular projection and said second annular projection, whereby the mechanical loading between said one pipe and said other pipe may be borne via said ball bearing means and the vacuum-tightness between the inner space of the pipe system and the environmental atmosphere may be maintained by means of said slidable vacuum seal means while admitting the relative rotation of the flanges and their associated pipes about the center axis of said flanges.
 6. A piping system in a vacuum degassing apparatus for molten metal including a ladle body suspended from movable suspension means disposed thereabove for receiving the molten metal poured from a lower end of an outlet trough of a furnace and adapted to be moved within a given vertical plane by said movable suspension means in accordance with the displacement of the lower end of said outlet trough which follows the process of pouring the molten metal; characterized in that said piping system comprises a mounting pipe fixedly secured onto an upper cover plate of said ladle body so as to communicate with an opening in said upper cover plate, a relatively fixed pipe connected to evacuating means, and a plurality of movable pipes connected with each other and with said mounting pipe and said fixed pipe, respectively, via a plurality of pairs of slidably and vacuum-tightly coupled flanges disposed in parallel to said given vertical plane and rotationally slidable about the axes of said respective flange pairs, said piping system being further characterized in that said piping system includes a second suspension means adapted to vertically suspend one of said movable pipes at one point Thereon, and comprising guide means, a truck adapted to travel forth and back along said guide means, reversible driving means for driving said truck, a rope having one end connected to said one point on the movable pipe and the other end connected to a counterbalance weight, pulley means mounted on said truck for supporting said rope, means for detecting an inclination of the rope section between said pulley means and said one point on the novable pipe with respect to the vertical, and control means responsive to detection of the inclination of said rope section for actuating the reversible driving means for said truck whereby to reduce the inclination of said rope section. 